The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)

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awemawson:
This morning I ran the two parts of the program that I split last night. But first I wrapped the 4th Axis in clingfilm to keep the machinable wax swarf out of it to save a bit of clean up time later.

First pass went very well, I was hovering with the workshop vacuum hoovering as the cut progressed as I don't want the wax in the machines coolant.

Second pass took ages to do not a lot until the very end. I'd had to specify a rectangular block of stock for it to cut. Although Featurecam allows for round stock I couldn't get the axis of the stock and the machining to be the same. In 3D view it looks perfect, but in plan they are misplaced - an oddity so hence rectangular stock and thus a lot of 'air cutting' before getting down to business. In the end the final cut was only about 0.5 mm and that (with all the air cutting) took 39 minutes !

I'm pleased with the results. I need to measure how accurately it's cut the 7 degree recess taper, I also need to replace the 22 mm 2 flute end mill for one with greater depth of cut - it manages but with very little margin - OK in the wax but probably pushing it in the final EN24T item.

nrml:
That looks really nice. Almost too good to melt and recycle. Is is it a taper lock fit?

Edit:
I've just gone back a few pages to look at the drawing of the spindle and I see the taper there. Sorry for the pointless question.

awemawson:
Thanks NRML, but . . .

No, the taper is a VERY relevant question as I have just realised that I mis-read the drawing, and what I understood to be a taper with limits of 7 degrees to 7 degree 30 seconds is ACTUALLY a taper of 7 degrees 7 minutes and 30 seconds (or 7.125 degrees).

I blame it on old eyes !

But this is what prototypes are for ! Imagine my chagrin if I'd gone straight to cutting that expensive EN24T billet !

I'm now wondering if Male lathe spindle nose tapers and Female chuck tapers are actually manufactured to slightly different angles. The bolting face obviously draws up tight with the taper as a register but manufacturing to get the taper an exact snug fit when the flanges are tightly together would be easier if one taper was very marginally different. Amazingly hard to find dimensioned drawings of the chuck female :scratch:

My aim today was to turn up an accurate male gauge for when I make the real thing, but other things have got in the way.

Muzzerboy:
That came out rather well. Good catch on the taper angle.

Do you plan to make some metal soft jaws? Presumably you will need something better than plywood for the real thing.

awemawson:
Thanks.

I am hoping to turn the taper on the Beaver TC20 along with a reference bore up the middle that I can use to accurately centre it on the Beaver Partsmaster with the Hiedenhain probe as a second op. for drilling the holes and other features. I can clamp it down for that operation. I only really milled the taper for a bit of fun to see how well it came out and the answer is surprisingly well, but you can feel ridges with your nail.

For boring the taper I took delivery of a nice heavy 32 mm boring bar today with integral though coolant :ddb:

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